java - eclipselink 缓存上的对象关系

Question

我有两个实体:

@Entity
public class CustomerMainInformation {
@Id @GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;

@Column(unique = true, length = 10)
private String customerNumber;
@OneToMany(mappedBy = "firstCustomerRelationship", cascade = CascadeType.ALL)
private List<CustomerRelationship> firstCustomerRelationship;

@OneToMany(mappedBy = "secondCustomerRelationship", cascade = CascadeType.ALL)
private List<CustomerRelationship> secondCustomerRelationship;
// setter & getter
}

@Entity
public class CustomerRelationship {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@ManyToOne
@JoinColumn(columnDefinition = "first")
private CustomerMainInformation firstCustomerRelationship;

@ManyToOne
@JoinColumn(columnDefinition = "second")
private CustomerMainInformation secondCustomerRelationship;

// setter & getter
}

我执行了以下代码:

    CustomerMainInformation customerMainInformation =manager.getReference(CustomerMainInformation.class, 1L);
    System.out.println(customerMainInformation.getFirstCustomerRelationship().size());
    System.out.println(customerMainInformation.getSecondCustomerRelationship().size());

    CustomerMainInformation customerMainInformation2 = manager.getReference(customerMainInformation.getClass(), 2L);
    CustomerRelationship customerRelationship = new CustomerRelationship();
    customerRelationship.setFirstCustomerRelationship(customerMainInformation2);
    customerRelationship.setSecondCustomerRelationship(customerMainInformation);
    manager.persist(customerRelationship);
    transaction.commit();

    EntityManager manager2 = factory.createEntityManager();
    CustomerMainInformation customerMainInformation3 =  manager2.getReference(CustomerMainInformation.class, 1L);
    System.out.println(customerMainInformation3.getFirstCustomerRelationship().size());
    System.out.println(customerMainInformation3.getSecondCustomerRelationship().size());

在此代码中，关系大小增加，但由于调用了 .getSecondCustomerRelationship() 之前，列表大小未更改。

如果 @Cacheable(false) 添加到 CustomerRelationship，则 .size() 返回正确的列表大小。

Answer 1

在显示的代码中，您似乎没有维护双方的关系。调用 setSecondCustomerRelationship 会设置它的一侧，这一侧控制着 db 中的外键字段。但是您的 java 对象模型与您的更改不同步，除非您还将 customerRelationship 添加到 customerMainInformation 的集合中。 JPA 不会为您维护关系，因此如果您更改一侧，您有责任保持另一侧同步。

您可以同时设置两侧，也可以在提交后强制从数据库刷新 customerMainInformation。第一个选项效率更高。